1. Technical Field
The invention relates to air springs and in particular to air springs having an internal bumper which acts as a backup in case of air spring failure or to absorb sudden large deflections or shocks imparted on the air spring. More particularly, the invention relates to an air spring having a snap-on plastic bumper replacing the heretofore used elastomeric bumper.
2. Background Information
Pneumatic springs, commonly referred to as air springs, have been used for motor vehicles and various machines and other equipment for a number of years to provide cushioning between movable parts, primarily to absorb shock loads imparted thereon. The air spring usually consists of a flexible rubber sleeve which extends between a pair of end members which contains a supply of compressed air and may have one or more pistons located within the flexible sleeve. The end members mount the air spring on spaced components or parts of the vehicle or equipment on which the air spring is mounted.
The internal pressurized fluid which is generally air, absorbs most of the shock impressed upon or experienced by one of the spaced end members by which the air spring is mounted, with the end members moving axially towards and away from each other upon absorbing the imparted shock. Examples of such air springs are shown in U.S. Pat. Nos. 4,852,861 and 4,946,144.
Certain of these prior art air springs have internal bumpers mounted on one of the end members which extends into the interior of the pressurized chamber The bumper prevents total collapse or deflection of the spring member in the event of air spring failure, or to absorb shock upon the spring experiencing severe shocks and deflections. Heretofore, these bumpers consisted of an elastomeric member which was mounted on a stud extending outwardly from one of the end members such as shown in U.S. Pat. Nos. 4,506,910 and 4,787,606. Although these elastomeric bumpers are satisfactory for most applications, the bumpers require a lubricant and special equipment to assemble the bumpers on the projecting studs. This results in additional cost for both the lubrication and assembly equipment.
Therefore, the need exists for an improved type of air spring bumper which eliminates the heretofore used elastomeric bumper and the expensive equipment required for mounting the bumper on its internal supporting stud.
Examples of other prior art showing shock absorbing components are set forth in the following patents.
U.S. Pat. No. 4,478,396 discloses an elastomeric bumper which is mounted on the top of a vehicle strut.
U.S. Pat. No. 3,658,314 discloses a fluid shock absorber having an elastomeric member mounted between two concentrically movable tubes with an elastomeric bumper mounted beneath the inner tube to absorb impact from the tube.
U.S. Pat. No. 4,342,264 shows another type of air spring using an elastomeric bumper mounted on one of the end members.
U.S. Pat. No. 4,218,599 discloses a polymer spring for use in a drawer of a cabinet to ensure that when the drawer is closed it does not rebound to a partially opened position.
However, no known prior art including those discussed above, disclose an air spring having an internal bumper which is formed of a plastic material and is snap-fitted into position on a bumper mounting stud to replace the heretofore used elastomeric bumpers.